jPlayer无法读取未定义的属性“海报”

Question

jplayer存在问题，我需要做的是，我想在上一首曲目结束后自动播放下一首曲目。 我的HTML为：

<div class="row-track active" data-track-id="30">
    <div class="row-holder" data-src="url/30">
        <span class="status">
        <a href="javascript:;" data-toggle="tooltip" title="" class="play-pause no-pjax addTrack audio-element" data-audio="mp3_url" data-waveform="img_url" data-id="30" data-album-id="74" data-title="Usually Suspect" data-artist="Ambient Drama" data-original-title="#7">play/pause
        </a>
        </span>
    </div>
</div>
<div class="row-track active" data-track-id="40">
    <div class="row-holder" data-src="url/40">
        <span class="status">
        <a href="javascript:;" data-toggle="tooltip" title="" class="play-pause no-pjax addTrack audio-element" data-audio="mp3_url" data-waveform="img_url" data-id="40" data-album-id="74" data-title="Usually Suspect" data-artist="Ambient Drama" data-original-title="#7">play/pause
        </a>
        </span>
    </div>
</div>

在jplayer中-> bind($.jPlayer.event.ended 我已经完成了：

 var nextSongId = $("div[data-track-id='"+event.jPlayer.status.media.trackId+"']").
            next().attr('data-track-id');
    var trackOnEnd = inPlaylist(nextSongId);
    demo.play(trackOnEnd);

    in demo.playlist I have an array of object.
    inPlaylist function is as follows:

    function inPlaylist(id) {
      var state = null;
      $.map(demo.playlist, function(elementOfArray, indexInArray) {
        if(elementOfArray.trackId == id) {
          state = indexInArray
        }
      });
      return state
    };

其中状态仅是对象在对象数组中的索引。 在某些地方，它工作正常。但是在某些情况下，它给我一个错误

  

无法读取未定义的属性“海报”